This invention relates to electrical devices for applying heat to the body of a person, and more particularly to electric heating pads constructed so as to remain flat when applied to a vertical body surface.
Electric heating pads are available in a variety of special configurations for special purposes, such as U.S. Pat. No. 3,953,671 for warming a cow's udder. The general public favors a simple planar, rectangular shape having a comfortable fabric outer surface, and sufficient flexibility for conforming to most body surfaces to which they are applied. These generally have their electrical resistance heating wire elements sealed within a water-tight rubber envelope, and have a large surface area that makes them versatile enough for most purposes. The pads in general use are sold with a warning to the user to avoid lying on the pad. When used in hospitals, nursing rules require that the patient must be sitting up or in prone position if this type of heating is applied to the back, and outpatients are instructed to follow these rules also. Back problems that can be temporarily relieved by application of heat are very common. Consequently, a most common use for electric heating pads is to the back while the user is sitting upright in a chair or bed. With the pad vertical between back and chair, any movement of the user may allow the pad to collapse or fold upon itself. When next the back is rested upon the crumpled pad, it is subjected to stresses that tend to break the wires, the user is subjected to concentrated heat below the useful area, and an uncomfortable bulge appears where once there was a smooth, flat, uniformly warm area.